I. Field
The disclosed embodiments relates to the field of communications. More particularly, the disclosed embodiments relate to control of signal power level for reducing interference, and efficient signal processing in a receiver for canceling signal interference.
II. Background
Code division multiple access (CDMA) communication systems have been in commercial operations for a number of years. In CDMA communication systems, a number of users in the same geographical area may choose to operate on a common carrier frequency. The signal from each user is coded according to a unique assigned code. A receiver receiving signals from the users with common carrier frequency decodes each signal according to the assigned code. While the signal is being decoded, the signals transmitted from all other users may be treated as interference. To control the interference level, one of the basic principles for operating a CDMA system is based on a method and apparatus for controlling the power level of signals transmitted by different users of the system. Other reasons, such as conserving battery power, for controlling power level of signals in a CDMA system are well known by one of ordinary skill in the relevant art.
Generally, to combat the effect of interference, a user may increase its signal power level, or the communication data rate, or both. As more users increase the signal power level or the communication data rate, the level of interference experienced by other users is also increased. As such, there is a need for controlling the power level of each signal transmitted by each user such that the interference level experienced by each user is minimized. Moreover, there is a need for efficient signal processing in a receiver for canceling signal interference.
A novel and improved method and apparatus in a communication system provides for efficient processing of received signals. The method and apparatus includes converting an encoded and spectrum spread received signal to received samples and determining a first channel estimate based on a first set of pilot signal samples. The first set of pilot signal samples are included in the received samples. The received samples are passed through a correlation and decoding process in accordance with the first channel estimate to produce decoded received samples. The decoded received samples are re-encoded and re-spread to produce re-encoded and re-spread samples. The re-encoded and re-spread samples are modified based on the first channel estimate to produce channel modified re-encoded and re-spread samples. The received samples pass through an interference cancellation process to produce a new set of received samples. The channel modified re-encoded and re-spread samples are used to perform the interference cancellation. As a result, decoding the new set of received samples produces less error.